1. Field of the Invention
The invention generally relates to ammunition and explosives. More specifically, the invention relates to blasting and terrain clearance. Another specific aspect of the invention relates to fuel air explosive. The invention is a device and method for artificially triggering an avalanche, such as a snow avalanche.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Avalanche control is a safety practice by which known snow slide areas are artificially triggered to release a snow slide or avalanche. Such artificial release reduces the possibility that an avalanche will occur at another time or in greater volume. Avalanche control is especially important in ski areas, where an unexpected avalanche might threaten human safety. Avalanche control also is important near mountain highways, where an unexpected avalanche might damage or close a road, in addition to threatening vehicles and human safety. Consequently, managing avalanches offers the advantage of causing the avalanche to take place at a planned, favorable time, such as when people and vehicles are not present and when any necessary machinery and equipment is available.
A basic method of releasing an avalanche is by use of an explosive to dislodge the snow. Various types of explosive charges are in use. Placing or throwing a charge of TNT is effective. However, such a method involves the difficulties and dangers of storing and directly handling explosives.
A method of avalanche control in common use in the United States is to fire an artillery shell at the snow slide area. The exploding shell can trigger an avalanche. If the avalanche fails to release, additional artillery shells can be fired. This method has the advantage of being simple, effective, and flexible. The artillery gun can be fired from a safe distance and repositioned as necessary to fire at additional snow slide areas. However, storing functional artillery guns and shells can be a public danger, since such equipment can be misappropriated and misused. For this reason, artillery guns and shells are being retired from use in avalanche control.
In 1975, the Washington University, Seattle, Dept. of Civil Engineering, reported a study titled “Alternate Methods of Avalanche Control,” published by the U.S. Department of Commerce. This study investigated several methods of releasing snow slides by mechanical action or explosive force applied from below the snow.
According to the first reported method, inflatable air bags were placed in known snow slide zones prior to snowfall. After snowfall, the air bags were inflated in an attempt to trigger the release of an avalanche. This method had many problems, including the inability to adjust bag placement once the snow layer was in place, various types of bag failures, and danger that the bags would slide with the avalanche.
In the second reported method, explosive gas was detonated in various types of chambers installed before snowfall. One device was a steel cylinder that constituted an explosion chamber. The chamber carried a movable lid mounted on guide rods and held by return springs. After snow had buried the chamber, explosive gas injected into the chamber was detonated to explosively raise the lid from the cylinder. The rising lid and escaping gas from the explosion disrupted the covering snow. In a second variation of an explosion chamber, a length of metal pipe was perforated with holes. After being buried by snow, the pipe was filled with explosive gas, which was detonated. The explosion passed through the perforations to directly disrupt the snow. In a third explosion chamber, a large truck tire and rim were used without a split ring so that part of the rim could move. The explosive gas was introduced into the tire and detonated. According to the study, these gas exploder systems were not uniformly reliable for triggering avalanches.
Other types of gas exploders deliver a detonation and shock wave above the snowfield. U.S. Pat. No. 5,107,765 to Schippers teaches the use of a gas gun in the form of an explosion chamber configured as a tank with a discharge port pointed in the direction of the slope where the avalanche is to be triggered. The gas gun must be solidly anchored to the mountainside. Anchoring such a gas gun to a sufficiently solid foundation is difficult, particularly where native rock is crumbling. Further, the vibrations from explosions in the gas gun tend to fracture the foundation, damaging the mountain environment and requiring periodic remounting of the gas gun. During winter conditions, likely it is impossible to rebuild a foundation for the gas gun, resulting in loss of avalanche control at the site for the remainder of the season.
U.S. Pat. No. 6,279,481 to Schippers discloses a device characterized as an explosive hammer for dislodging cornices. A structure likened to the hammerhead is an explosion chamber configured as a hollow cylinder with closed top and open bottom. A structure likened to the hammer handle is an arm connected to the hollow cylinder and anchored to a mountainside by a pivot. A foundation secures the end of the arm to the mountainside. After a cornice forms over the cylinder, the explosion chamber is filled with explosive gas, which is detonated. Upon detonation, the gas raises the explosion chamber from the ground. The gas can escape from the open bottom of the explosion chamber. The discharging gas and the rise and fall movement of the explosion chamber combine to dislodge the cornice. However, over time the stress from the confined explosion and the hammering motion of the cylinder are likely to degenerate local rocks or the foundation.
Explosion chambers present additional limitations. For safety, combustible gases and oxidizing gases are not mixed prior to the approximate time of the intended explosion. The two types of gas are fed into the explosion chamber, where a degree of mixing takes place. However, short term mixing tends to be imperfect, which can reduce explosive yield when the mix is detonated. The explosion chamber may further limit explosive yield by preventing access to ambient oxygen, which otherwise might supplement the imperfect mixing within the chamber.
U.S. Pat. No. 6,324,982 to Eybert-Berard et al teaches a one-time-use explosion chamber similar to a butyl rubber weather balloon to hold explosive gas above the snowfield. Detonating the gas in the balloon destroys the balloon and generates an aerial pressure wave for releasing an avalanche. Such a frangible explosion chamber offers an advantage, as the balloon suffers no problems with degenerating foundations. However, handling and positioning a large balloon in the typically windy conditions of a mountaintop cause this solution to be impractical. Also, mountain locations are notable for having many hungry rodents, which often eat plastic, rubber, and almost any other material they can gnaw. The balloons are to be preinstalled in containers on a mountain and connected to a gas supply tube system. Quite likely the balloons, any nonmetallic portions of the containers, and any nonmetallic gas supply lines would present a food source to the rodents and quickly become non-operational.
It would be desirable to create an avalanche control system that is conveniently used in the often-difficult conditions on a mountaintop, that enjoys the relative safety and convenience of using explosive gases, but that does not tend to fracture its foundation or the rock structures of the mountain.
It would be desirable to create an avalanche control system that employs a combustible gas mixed with an oxidizing gas, in which ambient oxygen is readily available to the mixture to ensure good explosive yield.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the method and apparatus of this invention may comprise the following.